Romulan commanders weren't evil because they were promoted. They were promoted because they were evil.

Being ruthlessly cold and calculating, and absolutely loyal to your superiors and a government that worked solely for cultural expansion at the expense of civilian prosperity was the only way to get a high ranking government job. It was the sort of government where anybody who opposed the party got secretly disappeared.

On Earth, well, depends what company you work for. Some companies promote based on competence, some based on politics, and some based on how good you are at keeping your illegal behavior secret. If you earned your promotion and aren't dumping chemicals into rivers or buying companies for the sole purpose of selling off their assets, you're fine.

The argument 'A Romulan's first duty is to the government' is the same as saying 'The CEO's first duty is to the shareholders'. It's technically correct but it doesn't excuse the immoral, harmful behavior it's invoked to justify.